Engineered stone slabs are a specialized, non-porous, high performance type of composite stone slab that emulates both the physical and visual properties of natural stone slabs. The term “composite stone” is very broad, and can be applied to any material that is formed by adhering stone particles together. The most common forms of composite stone, such as asphalt, normal cement, or polymer cement, are not intended to emulate natural stone, and do not even remotely approximate the physical properties or appearance of natural stone slabs.
Engineered stone slabs, on the other hand, are a very specialized sub-category of composite stone slab which, until the present invention, were fabricated exclusively using a specialized and highly expensive type of vacuum vibration press invented by M. Toncelli of Breton S.p.A, and marketed by Breton since the 1980's. More recently, copies of the Breton design have been manufactured and sold by other sources, but the Breton design remained the only design that could produce engineered stone until the present invention. Accordingly, engineered stone slabs are also sometimes referred to as “Bretonstone slabs.” Most commonly, a high percentage of the stone included in an engineered stone slab is quartz. Therefore, engineered stone slabs are also sometimes referred to as “Quartz slabs.” Other terms for this highly specialized type of stone slab are “ES-BS” (Engineered Stone-Breton Stone) slabs or “ES-BS-QS” (Engineered Stone-Breton Stone-Quartz Stone) slabs.
With reference to FIG. 1A, the slab mixture 126 used for fabricating ES-BS slabs typically includes about 55-65% stone granules 128, 22-30%-325 mesh stone powder, and between 6% and 10% resin binder, which is a liquid composed of resin, pigment, and additives. In specialized cases, mainly when crystobolite powder is substituted for quartz powder, the percentage of resin can go as high as 12% due to the very high surface roughness of crystobolite particles. Otherwise, the resin is typically 10% or less. This resin binder, combined with the −325 mesh powder, forms a binding paste 130 that binds together the stone granules 128 to form the ES-BS slab. A slab mixture containing more than 12% liquid is not, by definition, an ES-BS slab mixture.
Because of the relatively low percentage of resin binder in engineered stone (typically 6% to 10%), as compared for example to the relatively high amount of water or polymer binder in concrete, there is insufficient binder in an engineered stone slab mixture to fill all of the voids between the stone granules 128 as they are naturally arranged after mixing. As a result, an engineered stone slab mixture initially contains much entrained air 134. And because there is insufficient resin to fill the voids, gentle shaking and vibrating will only cause settling of the mixture, without eliminating the voids between the stone granules, and cannot transform an engineered stone mixture into a void-free article.
Accordingly, it is necessary when fabricating an ES-BS stone slab 132 to force the stone granules 128 in the slab mixture into a “close-packed” configuration, as illustrated in FIG. 1B, wherein the stone granules 128 are migrated under intense pressure and strong vibration from their natural, essentially random distribution, as shown in FIG. 1A, into a space-filling, close-packed arrangement that minimizes the total void volume between the stone granules 128, as is illustrated in FIG. 1B. If this close-packed stone granule configuration is not achieved, there will be insufficient binding paste 130 to completely fill all of the voids between the stone granules 128, and it will therefore be impossible to produce a non-porous slab having properties and appearance similar to natural stone slabs. At best, the result will be a porous slab with very poor qualities and appearance. The close-packed arrangement of the stone granules and the achievement thereby of a non-porous result, when the starting mixture contains too little resin to fill all the voids without close packing, is a defining feature of an engineered stone slab.
Definitions of Terms
Note that the following terms are used with the indicated definitions throughout this paper.
Composite Stone: Composite stone refers to all materials that are made by using some type of binder to glue together any type of stone materials, such as sand, gravel, marble, broken clay pieces, glass, mirror, quartz, or granite. Virtually any naturally occurring mineral or other inorganic material that is hard relative to the intended end use of the composite stone article can be used. There are many types of composite stone, including for example concrete, terrazzo, concrete blocks, concrete or cementitioius pavers and slabs, large concrete slabs as are used for manufacturing buildings or bridge decks, concrete road pavements, polymer concrete slabs and articles, decorative marble-based cementitious or resinous slabs, and finally, engineered stone slabs.
Engineered Stone slabs, also referred to as Bretonstone slabs, Quartz Slabs, (ES-BS) Slabs, or ES-BS-QS slabs. These terms are used synonymously herein to refer to a special class of composite stone slabs that contain very high (typically 90-94%) stone content and very low (typically 6-10%) resinous binder. The slabs are nonporous, having no voids in the interior or on the surface of the slab, and closely emulate the appearance and physical properties of natural stone slabs. Until the present invention, all such slabs were produced using a specialized and costly vacuum vibration press invented about 25 years ago by Breton S.p.A, and procured either from Breton, or more recently from other sources producing copies of the Breton design. The invention of engineered stone and the invention of the Breton press coincided, since the Breton press was designed specifically to produce engineered stone, and until the present invention engineered stone could only be produced using a press of the Breton design.
Stone Granules (SG), also referred to herein as granules or aggregates: This term refers generically to particles of stone (typically quartz or silica based stone), or of other hard materials (such as glass, granite, marble, and such like), having sizes in the range from about 0.2 mm up to 2-3 centimeters.
Quartz Powder (QP), also referred to herein as silica powder and filler: These terms refer to powdered material ranging in particle size from about 1 micron to about 300 microns in diameter. In the industry, QP is typically finely crushed and/or milled quartz or silica sand. It is readily available worldwide in a generally standard minus 325 (“−325”) mesh size, and can be made from marble (calcium carbonates), silica, quartz, glass, granite, or any other material that can be powdered and used for making quartz slabs. A special form of Quartz, known as crystobolite (made by heating quartz to over 1000 deg C.) is also used because of its unique whiteness. Due to the high surface roughness of crystobolite particles, and the correspondingly high oil absorption, an additional 1% to 2% resin is typically needed to wet the surfaces of the crystobolite granules, in addition to the 6% to 10% resin needed to fill in the gaps between the granules. Accordingly, for crystobolite-based ES-BS slabs, typically between 8% and 12% total resin is needed.
Resin: This term is used herein to refer to any resin and/or adhesive system capable of adhering together stone granules and quartz powder to form an engineered stone slab. Examples include epoxy, urethane, acrylic, vinyl ester, silicone resins, and even cementitious adhesives based on the various forms of hydraulic type cements. When the resin is a polyester material, then it may include various additives that affect the cure rate, and especially the adhesion of the resin to silica and/or quartz based minerals and granites. In the quartz slab industry, the resin is, for economic reasons, typically a modified polyester thermosetting resin.
Vacuum Vibration Press (VVP): This term is used herein to refer to an apparatus that can simultaneously apply sufficient pressure, vibration, and vacuum to an engineered stone slab mixture to force the stone granules in the mixture into a close-packed relationship that enables the limited amount of resin paste in the mixture to fill all of the remaining voids between the stone granules. It is the achievement of this close-packed configuration that enables the manufacture of an engineered stone slab. Until the present invention, the only type of VVP that was able to apply sufficient vibration and pressure to created close-packing of an ES-BS slab mixture was the Breton style of VVP and copies thereof.
It is important to note that the terms Vacuum Vibration Press, Vacuum Vibrating Press, and VVP as used herein do not apply to all types of press that can simultaneously apply pressure, vibration, and vacuum to a slab mixture. For example, polymer concrete slabs are sometimes manufactured by a press that applies small amounts of pressure, vibration, and vacuum to a PC slab mixture. However, such an apparatus would not meet the definition of a VVP as used herein, because the polymer concrete press would not be able to apply sufficient pressure and vibrational energy to an engineered stone slab mixture to achieve close-packing of the stone granules.
It should be noted that such NC-PC forming devices which include both vacuum vibration and pressing are very rare, because generally the vacuum and pressing functions are unnecessary for settling and flattening NC-PC mixtures. When vacuum vibration and pressing are employed by an NC-PC device, the amounts of vibration and pressing forces these devices apply are a tiny fraction of the forces required for close packing of ES-BS slab mixtures.
Close Packing (CP): This term refers to a tightly packed arrangement of the stone granules in an ES-BS slab mixture, which does not occur naturally, but can only be achieved by the application of strong pressure and vibrations to the mixture (as well as vacuum to remove the entrained air in the mixture). The applied pressure provides the “motivation” for the granules to become close-packed, and the very intense vibration causes the stone granules to move and “jiggle,” such that they are able to reorient and move past each other until a close-packed relationship is achieved. Achieving a close-packed arrangement of the stone granules in an ES-BS slab mixture is necessary for the production of ES-BS slabs.
Close Packing Energy (CPE): This term refers to a combination of high pressure and intense vibrational energy that is applied to the stone granules within an ES-BS slab mixture and is sufficient to force the stone granules in an ES-BS mixture to reorient and migrate into a close-packed arrangement. Until the present invention, the only press design that was capable of delivering CPE to an engineered stone slab mixture was the Breton design. Note that CPE is a combination of pressure and vibrational energy, and that different combinations of pressure and vibrational energy can provide CPE. Note also that the vibrational energy included in CPE is the vibrational energy that is present within the slab mixture, which will depend on the efficiency with which external “input” vibrational energy applied to the surface of the slab mixture is transmitted into the interior of the slab mixture.
Settling Energy (SE): this term refers to low to moderate vibration that is sufficient to cause a normal concrete mixture or polymer concrete mixture to settle, and to cause most air entrained in the mixture to rise to the surface, but is not sufficient to apply CPE to an engineered stone mixture. Note that the amount of SE that is required to settle a PC-NC slab mixture is dependent upon the total weight of the slab mixture being processed. Per square foot, the Settling Energy required for NC-PC slabs is only a small percentage of the CPE required for forming ES SLABS
SLAB: When this term is used herein in all capital letters, it refers to an engineered stone slab having an area of approximately 44 square feet, and a thickness of between 1 cm and 3 cm. This size of slab is standard in the industry. Older versions of the Breton VVP made slightly smaller slabs, and later models make slightly larger slabs. But, the term SLAB is used herein to refer to the standard 44 square foot, 1-3 cm thick size of engineered stone slab. A 1 cm thick SLAB weighs approximately 230 lbs, a 2 cm thick SLAB weighs approximately 460 lbs, and a 3 cm thick SLAB weighs approximately 700 lbs.
Pressing: This term is used herein to refer to the process of simultaneously applying vacuum, pressure, and vibration to an engineered stone slab mixture in a combination that provides CPE to the ES-BS slab mixture, and thereby forces the stone granules in the mixture into a close-packed arrangement. Until the present invention, the only style of VVP that could accomplish this was the Breton style press and copies thereof.
NC-PC composite stone: This term is used herein to refer generically to composite stone products in which the stone granules are not close-packed. Examples are “normal concrete” and “polymer concrete.” In an NC-PC slab mixture, sufficient liquid is provided to fill all the voids between the stone granules as they are naturally arranged when the slab mixture is first prepared. As a result, only very modest vibration, and possibly a small amount of pressure are required to level the mixture and to encourage any entrained air bubbles to rise to the surface and be eliminated.
NC-PC Vibrating Table: This term is used herein to refer to an apparatus that is designed to produce an NC-PC product, and which is not capable of applying CPE to an engineered stone slab mixture, even though it might be able to apply more moderate levels of vibration to an NC or PC slab mixture, possibly with vacuum, and in rare cases also with a small amount of pressure.
FIG. 1C illustrates the basic steps used to manufacture ES-BS slabs according to the Breton method. First, the slab mixture is prepared 100. Typically, this includes preparing a mixture containing about 65% stone granules 102 (small grains of 0.2 mm to 1 mm as well as aggregates pieces from 1 mm to 25 mm) such as crushed quartz, granite, mirror, and/or glass in granule sizes from 0.2 mm up to 6 mm or even 15 mm. About 25% “quartz powder” 104 is also included, where the term “quartz powder” generically refers to one or more powdered minerals such as silica and/or quartz (or crystobolite quartz powder), typically in an approximately minus 325 mesh (minus 45 micron) size. Finally, about 6 to 10% resin 106 is included, typically with additives such as catalyst 108, pigment blends 110, and dispersing media. It is also possible to make the ES-BS slabs with marble or calcium carbonate based powders and granules, although the finished product will have lower scratch/abrasion resistance and lower chemical resistance.
After the raw materials are weighed and measured, they are transported to a mixer 112 and mixed together 114. Typically, the mixer is charged with the stone granules, the resin, pigments, additives, etc are added, and the combination is mixed until the particles and granules are fully wetted. For purposes of color design, two, three, or more mixers may be employed, each with a different color of raw materials and pigments. This is illustrated in FIG. 2.
The quartz powder is then added while the mixing continues. When combined with the resin, the quartz powder forms a binding paste that serves as the binder between the stone granules. The mixed materials are then formed into a single slab 116, either in a rubber mold, a metal mold, or on a sheet of paper or other suitable carrier which can be used to transport the formed slab into the vacuum vibration press (VVP). Note that the order of addition of the various materials can sometimes be changed for efficiency or other reasons.
As illustrated in FIG. 1A, when the engineered stone mixture 126 is mixed and placed in the mold, there is insufficient resin and powder to fill all the voids between the stone granules, and so the mixture contains a significant amount of engrained air 134, and therefore functions as a 2-phase system, where Phase 1 is the grains and aggregate pieces 128, and Phase 2 is the binding paste 130. The mixture is difficult to move, and appears almost dry because of the small percentage of binding paste and the large percentage of stone granules. Entrained air will not and cannot “rise” out of the mixture 126 if only vibration is applied, because the resin and powder binder is so dry and rigid that it traps the air, and also holds the granules in their naturally occurring, “open” (i.e. not close packed) arrangement.
A void-free slab 132 can only be formed from the mixture if the stone granules are compacted into a close-packed configuration (see FIG. 1B), so that the two phases are merged.
Therefore, when the mixed material is spread and leveled in the mold, it is generally 15-50% thicker than the finished slab will be after pressing, because the granules 128 have not been forced yet into a close-packed relationship. For example, for a 2 cm SLAB, the spread and leveled material could be 2.3 to 3 cm thick before the pressing. If this mixture were processed in an NC-PC press, which would not be able to apply CPE to the mixture, the mixture after pressing would still be 10-30% thicker than if CPE had been applied, and would be porous, because the stone granules would be in a normal, non-compacted relationship, and so the mixture would still contain a significant amount of entrained air. Note that there is no existing NC-PC vibrating table or vibrating-press table that is able to apply even a small fraction of the pressure and vibration required to apply CPE to an engineered stone slab mixture.
Once the formed slab mixture 126 has been transferred to the press, it is simultaneously evacuated, vibrated, and pressed 118 in the Breton type VVP so as to compact the mixed material by forcing the granules into a close-packed arrangement 132, thereby minimizing the void volume between the granules 128 so that the small percentage of binding paste 130 is sufficient to fill all remaining space between the granules 128, so that there will be no voids 134 in the finished non-porous slab 132.
Once the slab has been pressed, it is transported to an oven or to some other location for curing 120. Depending upon the adhesive (resin) used to bind the particles together into the slab, the curing and hardening process can take place at ambient temperature or at an elevated temperature, and can require from a few minutes up to many hours. After curing and hardening, the slab is returned to room temperature (if heat has been applied).
The cured slab is then calibrated and polished 122 to a desired thickness and finish, using technology similar to what is used to grind, calibrate, and then polish conventional natural granite stone slabs. The final result 124 is a finished ES-BS slab that is non-porous and closely approximates the appearance and physical properties of natural stone slabs. Note that the presence of a single void on the surface of a slab will render the slab “second quality,” and more than two such voids will render the slab unsalable.
Disadvantages of the Breton VVP Design
The Breton vacuum vibrating press (VVP) is effective in producing ES-BS slabs because it delivers a combination of high pressing force and very high vibration energy that is sufficient to apply CPE to an engineered stone slab mixture, thereby forcing the stone granules into a close-packed arrangement. However, there are several disadvantages associated with the Breton style of VVP and procedure.
First, a Breton-style press 300 employs massive weight and power to simultaneously apply a vacuum, vibration, and downward pressure to the formed slab 312. Breton presses are therefore difficult to site and expensive to operate. With reference to FIG. 3A, the Breton press 300 includes a press cover/vacuum chamber 302 which is also the housing for vibrating motor 304 mounted to a vibration plate 306 and suspended by air bags 308 or similar vibration mounts. The press cover 302 is mounted on pneumatic posts 310 so that it can be lowered onto a formed slab material 312 which is typically brought into the press on a conveyer belt 314 running between the press cover and a press base 316. The steel vacuum chamber/press cover (302), which is typically shaped as a rectangular box, is massively built to withstand the vacuum force and the destructive long term effects of the intense vibration.
As seen in FIG. 3A, the press cover 302, which also contains the pressing mechanism and the vibrating press plate, is moved up and down with the hydraulic pistons 310. Because the downward pressure on the press plate during the vibration pressing cycle is up to 40 psi, then the hydraulic cylinders are required to hold the entire vacuum cover down, so as not to be pushed up (despite the 15 psi internal vacuum). As a result, the press cover 302 and included mechanisms 304, 306, 308 weigh between 10,000 and 15,000 pounds. In addition, the press base 316 weighs about 30,000 pounds. Altogether, the Breton press 300 typically weighs from 50,000 to 75,000 pounds.
In addition, a Breton press 300 must be anchored to a vibration-damped block 318 of concrete that is set beneath the concrete floor 320 and surrounded by a vibration isolating material 322. The vibration-damped block 318 is approximately 20′ long by 15′ wide by 20′ deep, and weighs another 300 tons. The press 300 plus the concrete block 318 “foundation” to which the press is anchored, form an “inertial base” weighing more than 325 tons, whose purpose is to force some of the applied vibration energy into the slab material, so that close packing can be achieved.
Without this enormous concrete block 318 and press base 316, close packing of the stone granules 128 would not result, because the applied vibrational energy would just pass through the SLAB, which only weighs 250-800 lbs, and would simply shake the base. Nevertheless, a Breton-style press has a very low energy efficiency. Even with the 325+ ton base as an inertial mass that resists the rapid vibration movement of the press plate 306, only a small percentage of the vibrational energy goes into the slab material 312 to accomplish the required close packing. This is partly because the massive base is only inertial, and is not actually a good “reflector” of vibrational energy back into the slab.
In addition, the more or less stationary inertial base also restricts and resists the movement and “jiggling” of grains and aggregate pieces in the slab, especially those grains and aggregate pieces that are near the bottom of the slab and close to the more or less immoveable inertial base.
Both of these problems must be overcome by applying a very high vibrational energy and pressure to the system. Because the formed slab 312 is positioned on a solid base 316 that is bolted to a concrete block 318, together weighing more than 325 tons, an enormous vibration force (about 90 KW per 45 sq foot SLAB or 2 kw per sq ft at 1000 to 5000 rpm) must be applied by a Breton-style press simultaneously with a static downward pressure on the vibrating press plate of 20-50 PSI, so as to properly vibrate and compress the SLAB. Essentially, to press and vibrate a quartz slab 312 weighing 250-700 pounds, the Breton press 300 is required to vibrate a mechanism 302, 316 weighing 50,000 to 75,000 pounds, plus the 300+ ton concrete block 318 it is bolted to. And still, only a modest amount of the applied vibrational energy is delivered into the slab to effect the close packing.
Also, there are incentives to apply more than just the minimum vibrational energy required to close-pack the slab. It is well known by ES-BS manufacturers, that when you apply more vibrational energy to a slab as it is pressed, then you can significantly reduce the amount of resin that is required, thereby saving cost (resin is expensive) and producing a slab more quickly and with even better appearance and physical properties. This can drive the energy costs still higher.
In addition, a Breton-style press imparts significant vibrations to the ground and surrounding structures. The entire Breton device, weighing more than 325 tons, is surrounded by foam vibration isolation walls 322, which isolate some of the vibration from the rest of the building. But in actual fact, the vibration from the device can be felt in the floor of the building from between 20 and 100 yards away.
Also, Breton-style presses are slow. The vacuum vibration cycle time per slab for a Breton press 300 is about 70-280 seconds, which reduces production throughput, and raises the operating cost. Also, a Breton-style press 300 costs about $6 to $7 million US dollars, which is very expensive.
Comparison Between PC-NC Slabs and Bretonstone Slabs
So as to fully understand the present invention and how it is distinguished from the prior art, it is important to understand the distinctions between engineered stone slabs and other types of composite stone products and the devices that are designed to make them, referred to herein generically as PC-NC products and vibration tables. The vast majority of composite stone materials, mainly concrete and polymer concrete, are produced for structural and/or industrial purposes, while engineered stone is produced mainly for decorative purposes. There have been a few attempts during the last 30 years to produce a decorative non-Bretonstone composite stone product, but they have been mainly unsuccessful. These include PBI, which failed in the decorative market; Granitech, which also failed in the decorative market; GRANIT 90, which is still produced but in very small quantities, and RESPECTASTONE, which is currently not in the market because of its high resin content and unsatisfactory appearance and physical performance as compared to Bretonstone.
Because the purpose, design, and effect of the ES-BS and of the PC-NC devices and products produced are so different, expertise in one area does not translate easily into expertise in the other area. Experts in the field of Polymer Concrete and Normal Concrete (PC-NC) and experts in the field of Engineered Stone do not normally discuss the distinction between these materials and their very different energy-principals of compaction, simply because the produced products are in entirely different categories as to use and manufacturing principals. Nevertheless, there are very important distinctions that must be understood in order to understand the present invention.
Normal concrete and cement type mixtures have a high liquid content, and are generally liquid, flowing, and easy to move. Air bubbles entrained in the mixture are often not a problem, because they tend to rise out of the mixture due to the high liquid content. Relatively low energy vibration, applied to the outside of the container or by placing the vibrator head into the mixture, is sufficient to remove the entrained air and settle the mixture into the desired shape.
Polymer concrete: These mixtures have a lower liquid content than normal concrete, because polymer is expensive, but the liquid content is still much more than for an engineered stone mixture, and is adequate to wet all the grains and pieces of aggregate in the PC mixture. A PC mixture normally flows easily, and can typically be leveled and formed by the application of very modest vibration, although vacuum degassing may be used to remove the entrained air, and in rare cases a mild pressure may be applied, typically when the PC slab must be pressed onto a form to create a non-flat shape.
With reference to FIG. 3B, in a normal concrete or polymer concrete mixture 324, after mixing, the stone granules 128 and smaller grains 326 are completely surrounded by a surplus of liquid 328, which is typically water, Portland cement slurry, or polymer. The mixture 324 is a single phase system, in that it is a liquid or semi-liquid “soup” containing more or less freely moving grains 326 and aggregate pieces 128.
Because there is sufficient liquid plus fine grains or powder to fill all the space between the grains 326 and aggregate pieces 128, an applied vacuum, or vacuum with moderate vibration, will cause any entrained air to rise to the surface and be removed, and will typically cause the mixture to flow into a mold, although sometimes gentle pressing is also applied, especially when forming non flat items. This combination of moderate vibration and pressure is referred to herein as “settling energy” or “SE.”
A typical SE vibrational energy would be in the range of 1-5 HP per PC SLAB. This vibrational energy can be delivered by any number of NC-PC vibrating machines manufactured by hundreds of companies. Application of additional strong pressing and vibration to a normal concrete or polymer concrete mixture, for example at a level equivalent to CPE, would not further compact the mixture, because the mixture does not include any voids that can be filled or any other mechanism that would allow for further volume reduction. To the extent that the larger aggregates pieces 128 are moved closer together by SE, normally to the bottom of the mold, because their density is higher than the polymer-powder or water/cement binder, this process is similar to vibration-assisted sedimentation, and does not result in any special close packing of the settled pieces, or any reduction in volume.
In contrast, in manufacturing an ES-BS SLAB, the Bretonstone type of VVP applies CPE that includes an input vibration energy of more than 100 HP per SLAB.
There is also a very large difference in the pressure that is applied by a PC-NC press as compared to an ES-BS press. Typically, for a PC-NC press the pressing is solely for the purpose of flattening the PC-NC slab mixture, or to press a form down into the material in order to create a 3-d shape such as a trough or basin. As discussed above, because a PC-NC slab mixture contains enough liquid and powder to fill all of the voids between the grains and aggregates, the mixture is not compressible in volume. Hence only a very modest pressure needs to be applied by the platen or mold. Typically, a PC-NC press need only apply one or two psi to the slab mixture to accomplish the desired result.
In contrast, forcing the stone granules of an engineered stone mixture into a close-packed relationship requires an ES-BS Breton-style press to apply very high pressure to the slab mixture at the same time as the intense vibrations (and of course the applied vacuum). Typically, a Breton ES-BS press must apply between 20 and 50 psi.
There is also a significantly different relationship between slab size and required vibrational energy for PC-NC slabs as compared to ES-BS slabs. In the case of PC-NC materials, if the article to be vibrated is of lower weight, then proportionally less vibrational energy is required. However, this is not true for ES-BS slabs. The same very intense vibrational energy that is required for a 700 lb 3 cm thick SLAB is also required for a 250 lb 1 cm thick SLAB. Why? Because in the case of ES-BS materials, only a very small percentage of the vibrational energy (and pressing) is used as SE energy to flatten or mold the mixture, while most of the vibrational energy is applied as CPE energy to force the close packing of the grains and aggregates pieces, irrespective of the slab's weight.
PC-NC devices and ES-BS VVP presses also differ typically in the number of vibration devices that are used. For Breton-style ES-BS presses, most manufacturers use a single vibration device on the top plate. However it is possible to place 2 or more vibrating devices on the top press plate, provided that they are mechanically or otherwise “linked” to function as a single unit of force in amplitude and frequency, and are required to have uniform vibration energy and waves across the entire slab. Due to the large concrete base beneath the press table, it is not possible to attach vibrating devices to the bottom of the press table. In contrast, PC-NC presses may include one or two synchronized vibration devices on the bottom of the slab tray in addition to one or more vibration devices on the sides of the slab tray to facilitate movement of the slab mixture, especially into complex shapes or molds, especially for large bridge decks or wall sections of reinforced concrete. But the use of said multiple vibration devices does not radically change the principals of the function and design of a PC-NC press.
What is needed, therefore, is a system for manufacturing engineered stone slabs that is much lower in weight, requires much less input vibrational energy, transmits much less vibration to surrounding structures, delivers more vibrational energy to the slab mixture, requires less resin, is faster, and costs significantly less to purchase, site, and operate than a Breton-style VVP.